Tyrosine kinase activity of a Ca2+/calmodulin-dependent protein kinase II catalytic fragment.
A 30-kDa fragment of Ca(2+)/calmodulin-dependent protein kinase II (30K-CaMKII) is a constitutively active protein Ser/Thr kinase devoid of autophosphorylation activity. We have produced a chimeric enzyme of 30K-CaMKII (designated CX(40)-30K-CaMKII), in which the N-terminal 40 amino acids of Xenopus Ca(2+)/calmodulin-dependent protein kinase I (CX(40)) were fused to the N-terminal end of 30K-CaMKII. Although CX(40)-30K-CaMKII exhibited essentially the same substrate specificity as 30K-CaMKII, it underwent significant autophosphorylation. Surprisingly, its autophosphorylation site was found to be Tyr-18 within the N-terminal CX(40) region of the fusion protein, although it did not show any Tyr kinase activity toward exogenous substrates. Several lines of evidence suggested that the autophosphorylation occurred via an intramolecular mechanism. These data suggest that even typical Ser/Thr kinases such as 30K-CaMKII can phosphorylate Tyr residues under certain conditions. The possible mechanism of the Tyr residue autophosphorylation is discussed.
Sugiyama
Yasunori
Y
Department of Life Sciences, Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kagawa 761-0795, Japan.
Ishida
Atsuhiko
A
Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan.
Sueyoshi
Noriyuki
N
Department of Life Sciences, Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kagawa 761-0795, Japan.
Kameshita
Isamu
I
Department of Life Sciences, Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kagawa 761-0795, Japan. Electronic address: kamesita@ag.kagawa-u.ac.jp.
D000595:Amino Acid Sequence; D000818:Animals; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000235:genetics / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D014981:Xenopus
D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2